Conference Agenda

Femtosecond direct laser writing as a 3D-printing technology has transformed the field of micro-optics. Over the last decade, complexity and surface quality of printed optical components have ever increased from simple micro-lenses⁠ to multi-element systems⁠, printed spectrometers and multimodal OCT-probes. This rapid development reflects the large potential and application range of 3D-printing technology. Especially medical applications, like OCT, fluorescence or endoscopy require small scale optical systems with high fidelity. But similar, industrial metrology or imaging applications can profit from the many degrees of freedom and miniaturization potential of this technology.

However, the almost unlimited design freedom regarding surface shape, microstructures, apertures and geometry has to be controlled during the optical design process under limiting manufacturing and material constraints. Due to the small size of only 10-1000 micron, moreover diffraction effects need to be considered by appropriate wave-optical simulations.

This paper highlights relevant aspects in the design and simulation of 3d-printed systems. It presents multiple design examples, ranging across micro-optical imaging-, illumination- and sensing-systems for various applications.

This contribution presents a method for producing serial junction heterogenous nanowires through three-dimensional(3D) printing of vertically freestanding nanostructures. Serial junction can be implemented by sequential printing of two different materials. One major issue is accurate positioning of the printing nozzle at the end of the pre-fabricated nanostructure for sequential printing of different material. Typically, nozzle-based direct printing method involves an optical microscope for positioning of the nozzle. However, optical microscopy often suffers from difficulties in identifying the position in the depth axis, distinguishing overlapped objects, resolving nanoscale features. In this study, we present a novel positioning method based on visualizing the nozzle tip with scattered light that is sensitive to contact. Direct 3D printing of PEDOT:PSS and P3HT serial junction heterogenous nanowire was demonstrated via precise positioning of the nanocapillary nozzle with the tip scattered light. Our direct printing method provides a simple route for producing heterogeneous junction nanowires in a position-selective manner, which can be used in light-emitting devices, image sensors, and solar cells.

Computer-generated volume holograms (CGVHs) contain 3D refractive index modulations designed to create complex-shaped wave fields for various optical applications. Two-photon polymerization (2PP) lithography is a single-step fabrication method for such CGVHs that allows the tailoring of refractive index distributions by applying locally varying printed powers. In this work, we fabricate 3D Ronchi gratings on top of modified optical fiber using two different printing powers. To expand the beam to illuminate the whole grating structure, we use coreless termination fiber (CTF). This approach paves the way for fabricating complex CGVHs on the fiber tip by tailoring refractive index distributions through controlled power variations.

Where diffraction orders propagate parallel to periodic structures, reflection and transmission spectra exhibit branch points. In the vicinity of these branch points, the spatial Fourier coefficients of the electromagnetic fields must be regarded as multi-valued functions and resonances from different Riemann sheets contribute. The square-root-like singularities at the branch points interact with resonances in a unique way that results in pronounced asymmetric Wood’s anomalies with discontinuous first derivatives. Multi-valued rational approximations can explain the shape of these features and can make the resonances on different Riemann sheets accessible.

Information extracted from a system’s quasi-normal modes—obtained via numerical solvers—should provide a means to reconstruct spectral expansions of photonic response functions (like the $T$-matrix). These spectral representations provide broad-band frequency predictions which should, in principle, even provide efficient time-domain simulations. However, time-domain implementations are typically constrained by the practical requirement of truncating the infinite spectral expansion, which introduces non-physical predictions, particularly at frequencies far from the region of interest. In this work, we show how physical and mathematical bounds on the response functions can be used to systematically adjust the spectral residues, thereby compensating for the effects of truncation.